Equipment for subsurface autofluorescence spectroscopy

ABSTRACT

An equipment includes an excitation source ( 1 ), elements for injecting ( 2 ) an excitation signal produced by the source in an ordered bundle ( 3 ) of flexible optical fibers, elements for analyzing ( 21, 22 ) an emitted autofluorescence signal. The equipment also includes at the output of the optical fiber bundle ( 3 ) an optical head ( 4 ) designed to be placed in contact with the biological tissue ( 6 ), the optical head being equipped with optical elements adapted to cause the excitation signal output from the bundle ( 3 ) to converge into a subsurface analyzing zone ( 5 ), the same optical fiber(s) used for excitation of the bundle ( 3 ) being used for detecting the signal emitted by the subsurface analyzing zone, elements (D) placed upstream of the injection elements ( 2 ) being further provided to separate the wavelength of the excitation signal and the wavelength of the autofluorescence signal.

BACKGROUND OF THE INVENTION

The present invention relates to an equipment for subsurfaceautofluorescence spectroscopy. More particularly, the equipmentaccording to the invention is of the type using an excitation signalcarried by one or more flexible optical fibres.

DESCRIPTION OF THE RELATED ART

The fields of application of the invention are in-vivo spectroscopicbiological tissue analysis, on humans or animals, external or internaland accessible using the instrument channel of an endoscope into whichthe optical fibres can be introduced, and also the ex-vivo analysis oftissue samples from biopsies, and the in-vitro analysis of cultures incell biology.

At present the medical fields of gastroenterology, respirology,gynaecology, urology, otorhinolaryngology, dermatology, ophthalmology,cardiology and neurology are concerned.

Biological tissues contain endogenous fluorophores capable, in responseto a luminous excitation of appropriate wavelength, of emitting afluorescence in a spectral range from close to the UV to the visible,called autofluorescence. The latter results from the recovery ofemissions from different fluorophores, and depends on the cellmetabolism, structure and vascularization of the tissues, which varydepending on the healthy or tumorous nature of the tissues. As a resultthe fluorescences from healthy and tumorous tissues have strongdifferences with respect to both the intensity emitted and the form ofthe spectrum. Analysis of the autofluorescence spectrum providesindicators allowing an “optical biopsy”.

In existing equipments, the illumination of the site to bespectroscopically analyzed is commonly carried out with an excitationoptical fibre bundle which is divergent, exciting a volume, and thereception of the fluorescence signal is carried out by means ofadjacent, in particular peripheral, detection fibres. This leads to apoor resolution, with a mixture of information and an increase in thenumber of false positives.

The present invention aims to overcome these drawbacks.

Moreover confocal imaging techniques with high spatial resolution havebeen proposed, intended for observing a section plane XY at differentdepths of the observed site, in particular disclosed in the PatentApplication WO OO/16151.

These techniques use an organized bundle of flexible optical fibres (inparticular several tens of thousands) with, on the observer's side, alight source and a system for injecting fibres allowing illumination ofa single fibre and, on the side of the observed site, an optical headallowing focussing of the beam leaving the illuminated fibre into apoint situated in a section plane XY, at a given depth of the observedsite. A fibre scanning system allows scanning of the fibres one by oneat very high speed. Each fibre is used alternately for carrying theillumination beam and also used for the corresponding return beamoriginating from the observed site. The obtaining of a high spatialresolution is due to the fact that the beam is focussed into a point andalso to the confocal character residing in the spatial filtering of theobserved site by the same fibres as those having served for theillumination. This makes it possible to receive exclusively the signaloriginating from the observed site and to produce an image point bypoint.

SUMMARY OF THE INVENTION

The present invention aims to propose equipment which allows aspectroscopic analysis also with high spatial resolution and at a givendepth of the observed site.

It proposes equipment for spectroscopic analysis of autofluorescence ofa biological tissue comprising an excitation source, a bundleconstituted by a single flexible optical fibre or a plurality offlexible optical fibres and means for injecting an excitation signalproduced by said source into said bundle according to a useful diametercorresponding to the excitation of the single fibre, all the opticalfibres in the bundle or a specific sub-group, and a means for analyzingan emitted autofluorescence signal, characterized in that it comprisesat the output of said flexible optical fibre bundle an optical headintended to be placed in contact with the biological tissue, saidoptical head being equipped with optical means adapted for convergingthe excitation signal coming out of said flexible optical fibre bundleinto a subsurface analysis zone, the same optical fibre or fibres ofsaid bundle having served for the excitation being used for detectingthe signal emitted by said subsurface analysis zone, means placedupstream of the means for injecting being moreover provided forseparating the excitation signal wavelength and the emittedautofluorescence signal wavelength.

The present invention is thus based on certain of the means mentionedabove for producing a confocal image, namely carrying on the same fibresor fibres the excitation signal and the emitted return signal, and theuse of an optical head focussing the excitation signal into a point at adepth. The focussing combined with the confocal character (obtainedthanks to the return of the autofluorescence signal by the same opticalfibre or fibres), makes it possible to obtain a high spatial resolution.The advantage compared with wide field spectroscopy is that a veryprecise spatial selection of the analysis zone can be carried out andthe likelihood of errors and false positives is thus greatly reduced.

The optical means of the optical head comprise a system of lensesforming a focussing objective adapted for transcribing the spatialdistribution of the focal spot at the fibre bundle output and fortranscribing the quality of the wave front, and adapted for minimizingthe parasitic reflection occurring at the fibre bundle output.

According to the present invention, the number of optical fibres in thebundle can vary between a single fibre and a plurality of fibres (inparticular several tens of thousands) being able to be excited alltogether or by sub-groups selected according to the dimensions of theexcitation zone sought.

The excitation zone according to the invention is situated in a plane XYperpendicular to the optical axis which can be adjusted to differentdepths, ranging approximately from 50 to 400 μm. Its dimension dependson the diameter of all of fibres used (hereafter called the usefuldiameter of the fibre bundle), and the optical focussing characteristicsof the optical head. When a bundle constituted by a multitude offlexible optical fibres is used, the equipment can advantageouslycomprise means allowing adjustment of the diameter of the excitationbeam emitted by the source so that it continuously excites either all ofthe fibres or a sub-group of fibres making it possible to obtain anappropriate size for the excitation zone. These means are for exampleconstituted by a beam adaptation lens or an afocal system withappropriate magnification.

The present invention also proposes equipment comprising moreover meansmaking it possible to jointly obtain a confocal image of the analysissite. Such a coupling possibility makes it possible to advantageouslyincrease the degree of certainty of a diagnosis. Thanks to theinvention, it is possible to obtain simultaneously and in real time,relative to a focussed point at a depth, information:

-   -   of histological type by confocal imaging; and    -   of spectroscopic type concerning the nature of the observed        site.

It proposes equipment as defined above, the fibre bundle comprising aplurality of optical fibres, characterized in that it comprises moreovermeans for jointly producing a confocal image of the analysis zone,comprising:

-   -   an illumination source,    -   a detector of the return signal for analysis,    -   a means for separating the illumination signal and said return        signal,    -   means for coupling the excitation signal for the spectroscopic        analysis and the illumination signal for the confocal imaging,        before introduction into the means for injecting into the        optical fibre bundle,    -   a means for rapid scanning of the fibres one by one situated        upstream of the means for injecting into the fibre bundle, and    -   a spatial filtering system at the signal detector input adapted        for selecting the return signal originating from the illuminated        fibre,

the means for injecting into the fibre bundle having a spatialdistribution of the focal spot intensity equal to the diameter of afibre core, each fibre being illuminated alternately and in an addressedmanner.

According to the invention, the tomographic and spectroscopic routesadvantageously share the means for injecting into the fibre bundle, thefibre bundle itself and the optical focussing head. For the acquisitionof an image, the fibres are illuminated alternately and one by one. Forthe acquisition of an autofluorescence spectrum, the fibres can beexcited all together or by sub-groups, as a function of the dimensionsof the analysis zone.

The use of a flexible optical fibre bundle can be advantageous for asystem of automatic tests in which advantageously the fibre bundle, withthe optical head at its end, is manipulated automatically as a measuringarm on a matrix of samples.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood and other advantageswill become evident in light of the description which follows of twoembodiments, which description refers to the drawings in which:

FIG. 1 illustrates diagrammatically a first embodiment of spectroscopyequipment according to the invention;

FIG. 2 illustrates diagrammatically a second embodiment of equipmentcomprising a spectroscopic analysis and confocal imaging coupling; and

FIG. 3 illustrates diagrammatically an embodiment variant of theequipment of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the embodiment chosen and represented in FIG. 1, anequipment is proposed for producing a subsurface spectroscopic analysisat a given depth, comprising a source 1 producing an excitation signal,a means for injecting 2 said signal into an organized optical fibrebundle 3 at the end of which is arranged an optical head 4 adapted formodifying the excitation signal leaving said optical fibre bundle 3 inorder to create a convergent beam focussed on a zone 5 underlying thezone of contact 6 with the optical head 4.

The source 1 used is chosen in order to allow excitation of theendogenous fluorophores present in the biological tissues of theobserved site, in particular in a wavelength range of 300-500 nm.Typically a 405+/−10 nm diode laser can be used. Other sources such assolid lasers or gas lasers with or without harmonic generators can alsobe suitable with other wavelengths in order to excite other endogenousfluorophores.

The equipment comprises a means for adapting 8 the beam emitted by thesource 1 comprising here a lens L1 which is correctly coupled to themeans for injecting 2 into the optical fibre bundle 3. The opticalcombination allows adaptation of the size of the laser beam to theuseful diameter of said optical fibre bundle 3, corresponding to all ora sub-group of fibres effectively used. Moreover it makes it possiblehere to increase the diameter of the focal spot at the input to thefibre bundle 3 and as a result to increase the size of the spot formedon the tissue. This makes it possible to reduce the irradiance (i.e. thequantity of power per surface unit) on the tissue, and thus to respectthe standards of illumination of biological tissues.

The equipment also comprises a means adapted for separating twowavelengths, the excitation wavelength and the emitted autofluorescencesignal. A dichroic plate D is used here to this end achieving maximaltransmission at the illumination wavelength and a maximal reflection inthe fluorescence spectral range.

The signal at the excitation wavelength is directed at the output of theplate D towards the optical means for injecting 2 into the fibre bundle3. This means should have the minimum number of aberrations and shouldnot degrade the quality of the wave front in order to produce a focalspot close to the diffraction limit in order thus to produce an optimalcoupling with the fibre bundle 3. The means chosen here is constitutedby a custom-made doublet L3 and a standard triplet L4. The doublet L3allows correction of the residual aberrations of the triplet L4, namelythe curvature of field. Any other optical system having a wave frontquality WFE (“Wave Front Error”) of the order of λ/8 and a spatialdistribution of the focal spot intensity PSF (“Point Spread Function”)equal to the useful diameter of the fibre bundle 3 can be suitable.

The fibre bundle 3 allows access to the analysis zone by off-setting thesource 1. For endoscopic use, it should have a diameter and a radius ofcurvature allowing easy insertion into the instrument channel of theendoscope, which is a few millimeters in diameter in accordance withclinical use (between 2 mm and 4 mm). It is possible to use a bundleconstituted by a single flexible optical fibre or a plurality of fibres.In practice, the useful diameter can be chosen as a function of thefocal spot of the optical head, for example so that it is of the orderof several hundreds of microns, in which case it is known that thenature of the biological tissue observed does not differ from one cellto another.

At the fibre bundle 3 output, the excitation signal passes through theoptical head 4. The latter comprises several optical means, allowingconvergence of the excitation signal, and two glass plates (notrepresented in the figures), one shared with the fibre bundle 3 outputand the other in contact with the tissue in order to produce an indexadaptation with the biological tissues.

The optical means have the following characteristics:

-   allowing analysis of the tissue at a depth of several tens to    several hundreds of microns;-   minimization of the aberrations in order to transcribe the PSF at    the fibre bundle output onto the tissue without enlarging the latter    or deforming it;-   optimization of the return coupling level in the fibre bundle by    optimizing the quality of the wave front;-   minimization of the parasitic reflection occurring at the fibre    bundle output by the integration of a glass plate.

Moreover, if it is an optical head intended for an endoscope, itsdimensions should be compatible with that of the instrument channel ofthe endoscope.

The optical focussing unit is constituted by a system of lenses with orwithout unitary magnification, forming a custom-made objective or asystem comprising for example two microscope objectives.

According to the invention, the fibre or fibres of the bundle 3 alsohave the function of detecting the signal emitted by the subsurface zone5. At the fibre bundle output 3, the signal detected is, as has beenseen, reflected by the dichroic plate D and directed towards the slit 21of a spectrograph 20. The coupling of the fluorescence signal to theslit 21 of the spectrograph is achieved thanks to an achromatic doublet.As a variant, any other achromatic optics can be used, the analysis ofthe fluorescence signal being carried out over a wide spectral range(350 nm-650 nm). A high-pass filter 22 thus allows elimination of theexcitation wavelength (the light backscattered by the tissue at the samewavelength as the excitation wavelength is in fact much greater than theautofluorescence light of the tissues which is produced at higherwavelengths). As a result, in order not to saturate the detector, thelight backscattered is blocked by the high-pass filter and a lens L2,placed upstream of the high-pass filter 22, allows improvement of thesignal-to-noise ratio by enhancing the signal detected by adaptation ofthe return beam to the dimensions of the slit 21.

The spectrograph 20 is chosen in order to have a wide numericalaperture, a cooling-down by the Peltier effect, a low noise level inorder to improve the signal-to-noise ratio, as well as a good spectralresolution (of the order of 3 nm). Means for displaying the spectrum,and of analyzing and processing are moreover provided.

FIG. 2, shows diagrammatically the equipment of FIG. 1 to which aconfocal imaging system has been advantageously coupled. The equipmenttherefore comprises a spectroscopic route which corresponds to thatdescribed with reference to FIG. 1 (the same references are used) and anadditional tomographic route making it possible to produce inconjunction a confocal image of the analysis site. The two routesadvantageously share the optical fibre bundle 3 and the optical head 4,as well as the means for injecting 2 into said fibre bundle 3.

Specifically, in order to obtain a confocal image point by point, theequipment uses here a bundle 3 comprising several optical fibres whichare illuminated one by one and alternately, in an addressed manner. Anybundle having enough fibres and a small inter-core spacing can be usedin order to obtain a good spatial resolution. By way of example, aSumitomo® strand of optical fibres can be used constituted by 30,000fibres with a core diameter of 2.5 μm and inter-core spacing of 4 μm, ora Fujikura® strand constituted by 30,000 fibres with a core diameter of2 μm and inter-core space of 3.7 μm. Such fibre bundles are compatiblewith endoscopic use. For the spectroscopic route, the acquisition of thespectrum with such fibre bundles takes place over the totality of thefibres of the bundle which corresponds to an analysis zone of severalhundreds of microns in which the nature of the tissue does not differfrom one cell to another.

Also specifically, the optical head is adapted for confocal imagingfibre by fibre making it possible to obtain a focussed analysis zone 5of the order of 0.5 mm in diameter in an analysis section plane XY.

Upstream of the fibre bundle 3, the tomographic route comprises a source30 constituted by a 683 nm laser diode and having a very good wave frontquality. This diode is pulsed in order to split by synchronous detectionthe useful signal from the parasitic reflection occurring at the inputto the fibre bundle 3. A solid or gas laser could also be used, but thechoice of wavelength in the 600-800 nm band where the absorption intothe tissues is lower, is less extensive; Moreover, the equivalent powercost is much greater.

In order to separate the illumination signal and the return analysissignal, a means for separating is used, constituted here by a 50/50separating cube 31 for adjustment facilities. A 50/50 separating platecan also be used.

The equipment comprises a scanning system 32 the aim of which is toreproduce a matrix of diodes of the same optical quality as the laserdiode of the source and which will be injected fibre by fibre. Thisrequires a combination of non standard optical means allowing correctionof the aberrations present in the transport and source duplicationsystem in order to illuminate the bundle 3 fibre by fibre. Thispoint-by-point imaging technique (each point corresponding to theillumination of one fibre) makes it possible to obtain a confocal imageof very good quality and at an appropriate image speed (15 images/s).

The scanning system is constituted by two mirrors M1 and M2, one is amirror resonating at a frequency of 4 kHz or 8 kHz, the other agalvanometric mirror with a variable frequency between 0 and 300 Hz, andtwo optical systems each constituted by four lenses, respectively L5,L6, L7 and L8, and L9, L10, L11 and 12 allowing first conjugation of thetwo mirrors, then the mirror M2 and the fibre bundle 3 input. Theseoptical systems should not have aberrations which could:

-   widen the PSF after the injection system and thus degrade the    coupling in the fibre bundle 3;-   propagate flux in the sheath which would degrade the PSF at the end    of the fibre bundle 3 and therefore the resolution of the equipment.

Unlike the equipment of FIG. 1, the means for injecting 2 into the fibrebundle 3 should have here a PSF equal to the diameter of a fibre core inorder to be able to produce an optimal coupling with a single fibre.

The lenses L6-L7 and L10-L11 of the scanning system 32 are two identicalcorrective doublets placed symmetrically relative to the image plane.They make it possible, with the doublet L3 of the system for injecting 2to obtain an image of very good quality by eliminating the residualaberrations of the optical combination of L5, L8, L9, L12 and L4, and touniform the coupling level in the fibre bundle 3 by eliminating thecurvature of field. They also therefore make it possible to improve thespatial resolution of the equipment by forming a spot with a PSF equalto the core diameter of the fibres, which does not lead to lightpropagation in the sheath of the fibre bundle 3, and therefore a PSF atthe output of said bundle 3 identical to that at the input.

The equipment comprises a spatial filtering system constituted by a lensL13 and a filtering hole 33 making it possible to select only theillumination fibre and not the adjacent fibres which can generate aparasitic signal. The size of the filtering hole is such that itcorresponds to the diameter of a fibre core, taking into account themagnification of the optical system, between the input to the fibrebundle 3 and the filtering hole 33.

The fibre bundle 3 is equipped at both ends with a glass platesufficiently thick and with an index sufficiently close to that of thefibres in order to reject the parasitic reflections outside thefiltering hole placed in front of the detector regarding the reflectionoccurring at the input to the fibre bundle 3, and outside the opticalfibres illuminated regarding the reflection occurring at the output ofthe fibre bundle 3. The glass plates have undergone anti-reflectiontreatment in order to minimize the light reflected.

As signal detector 35 an avalanche photodiode is used which acquires thesignal continuously, which makes it necessary to carry back theparasitic signal originating from the two ends of the fibre bundle 3with the same order of magnitude as the useful signal in order not tosaturate the detector. The elimination of the parasitic reflectionresidue at the input of the fibre bundle 3 is then carried out bydigital time filtering. Any other monopixel photodetector such as thephotomultiplier can be used, the advantage of the avalanche photodiodebeing its quantum yield of detection which is higher than that of otherdetectors.

In order to proceed with the coupling of the two confocalimaging/spectroscopy routes which is carried out with two differentwavelength sources, a dichroic plate D2 reflecting the red andtransmitting the blue and the green is used. The coupling could also becarried out with transmission in the red and reflection in the blue andthe green, but it has less optimal reflection and transmission levels inthis way.

In operation, the acquisition of a spectrum can be carried outsimultaneously with the acquisition of a tomographic image. Theequipment comprises means for analyzing and processing which allow adigital image to be recreated from the signals detected by the signaldetector 35.

The spatial resolution which can be obtained is of the order of 5 μm. Itallows in particular the diagnosis of pre-cancerous lesions based on thesize, form and density of the nuclei observed.

FIG. 3 shows an embodiment variant of the equipment of FIG. 2. Theidentical elements bear the same references in the two figures.According to this variant, the coupling of the two confocalimaging/spectroscopy routes is carried out upstream of the scanningmeans 32. To this end, the dichroic plate D2 is placed upstream of themirror Ml. The advantage of this construction is that it allows use ofthe scanning means 32 for displacing an excitation beam emitted on thespectroscopic route that has a smaller useful diameter than the totaldiameter of the fibre bundle 3, in order to inject it at a differentposition on the input surface of the bundle 3. This allows for exampledisplacement of the spectroscopic analysis zone in order in particularto make it corresponds to an image zone obtained by the confocal imagingroute.

As a variant also, which can be applied to the equipment of FIGS. 1 to3, as a replacement for the adaptation lens L1, an afocal system can beprovided allowing modification of the size of the excitation beam inorder to make it correspond to a given sub-group of optical fibres inthe bundle 3.

1. Equipment for spectroscopic analysis of autofluorescence of abiological tissue comprising: an excitation source (1), a bundle (3)constituted by a single optical fibre or a plurality of flexible opticalfibres, means for injecting (2) an excitation signal produced by saidexcitation source into said bundle according to a useful diametercorresponding to the excitation of the single fibre, all the opticalfibres in the bundle or a specific sub-group, and a means for analyzing(21, 22) an emitted autofluorescence signal, an optical head (4) at saidbundle (3) output, said optical head (4) intended to be placed incontact with the biological tissue (6), said optical head being equippedwith optical means adapted for converging the excitation signal comingout of said bundle (3) into a subsurface analysis zone (5), the sameoptical fibre or fibres of said bundle having served for carrying theexcitation signal being used for detecting the signal emitted by saidsubsurface analysis zone, and means (D) placed upstream of the means forinjecting (2) provided for separating the excitation signal wavelengthand the autofluorescence signal wavelength.
 2. Equipment according toclaim 1, wherein the optical means of the optical head (4) comprise asystem of lenses forming a focussing objective adapted for transcribingthe spatial distribution of the focal spot (PSF) at the fibre bundleoutput and the quality of the wave front (WFE) and for minimizing theparasitic reflection occurring at the fibre bundle output.
 3. Equipmentaccording to claim 1, wherein the optical head (4) comprises a glassplate intended to come into contact with the biological tissue to beanalyzed and adapted for producing an index adaptation with said tissue.4. Equipment according to claim 1, further comprising: a glass plateplaced at the output of the optical fibre bundle (3) and shared with theoptical head (4), said plate being sufficiently thick to reject theparasitic parallel reflections at the output of said fibre bundle (3).5. Equipment according to claim 1, wherein the means for injecting (2)into the optical fibre bundle (3) has a wave front quality and a spatialdistribution of the focal spot intensity adapted to the useful diameterof the fibre bundle (3).
 6. Equipment according to claim 1, wherein theexcitation source (1) emits at a wavelength adapted to excite chosenendogenous fluorophores present in the biological tissues of theobserved site.
 7. Equipment according to claim 1, wherein for separatingthe wavelengths is a dichroic plate (D).
 8. Equipment according to claim1, wherein the means for spectroscopic analysis comprise a spectrograph(20) and a means of coupling (21) to the slit of the spectrograph. 9.Equipment according to claim 8, wherein the means for coupling (21) tothe slit of the spectrograph comprises an achromatic optical means. 10.Equipment according to claim 8, further comprising: a means forrejecting (22) placed upstream of the coupling means (21) and adaptedfor eliminating the backscattered excitation wavelength.
 11. Equipmentaccording to claim 10, further comprising: a lens (L2) placed upstreamof the means for rejecting (22) adapted for improving thesignal-to-noise ratio.
 12. Equipment according to claim 1, furthercomprising: a means for adapting (L1) the size of the beam emitted bythe excitation source (1) to the useful diameter of the optical fibrebundle (3).
 13. Equipment according to claim 1, wherein the fibre bundle(3) comprising a plurality of optical fibres, further comprises meansfor jointly producing a confocal image of the analysis zone (5),comprising: an illumination source (30), a detector (35) of the returnsignal for analysis, a means for separating (31) the illumination signaland said return signal, means for coupling (D2) the excitation beam forthe spectroscopic analysis and the illumination beam for the confocalimaging, before introduction into the means for injecting (2) into theoptical fibre bundle (3), a means (32) for rapid scanning one by one ofthe fibres situated upstream of the means for injecting into the fibrebundle (3), and a system for spatial filtering (33) at the input to thesignal detector (35) adapted for selecting the return signal originatingfrom the fibre illuminated, the means for injecting (2) into the fibrebundle (3) having a spatial distribution of the focal spot intensityequal to the diameter of a fibre core, each fibre being illuminatedalternately and in an addressed manner.
 14. Equipment according to claim13, wherein the means for coupling are placed upstream of the scanningmeans (32).
 15. Equipment according to claim 13, wherein theillumination source (30) is a pulsed laser diode.
 16. Equipmentaccording to claim 13, wherein the illumination source has a wave frontquality of the order of λ/8.
 17. Equipment according to claim 13,wherein the detector (35) of the return signal is an avalanchephotodiode.
 18. Equipment according to claim 13, wherein the means forcoupling (31) the excitation signal for the spectroscopic analysis andthe illumination signal for the confocal imaging, comprise a dichroicplate (D2).
 19. Equipment according to claim 13, wherein the means (32)for rapid scanning of the fibres one by one comprises a mirror (M1)resonating at a given frequency and a galvanometric mirror (M2) with avariable frequency, and two optical systems each constituted by lenses(L5-8, L9-12) first adapted for conjugating the two mirrors (M1, M2)then the galvanometric mirror (M2) and the fibre bundle (3) input. 20.Equipment according to any claim 13, wherein the spatial filteringsystem comprises a filtering hole (33) the size of which is such that itcorresponds to the diameter of a fibre core, taking into account themagnification of the optical system, between the fibre bundle (3) inputand the filtering hole (33).